Midrapidity production of π ± , K ± , and (p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √ s NN = 5.02 TeV, is presented. The invariant yields are measured over a wide transverse momentum (p T) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0-90%. The comparison of the p T-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √ s NN = 2.76 TeV show no significant energy dependence. Blast-wave fits of the p T spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π , K/π) as a function of p T show pronounced maxima at p T ≈ 3 GeV/c in central Pb-Pb collisions. At high p T , particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √ s NN = 2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high p T and compatible with measurements at √ s NN = 2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.

The first evidence of spin alignment of vector mesons (K Ã0 and ϕ) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element ρ 00 is measured at midrapidity (jyj < 0.5) in Pb-Pb collisions at a center-of-mass energy (ffiffiffiffiffiffiffi ffi s NN p) of 2.76 TeV with the ALICE detector. ρ 00 values are found to be less than 1=3 (1=3 implies no spin alignment) at low transverse momentum (p T < 2 GeV=c) for K Ã0 and ϕ at a level of 3σ and 2σ, respectively. No significant spin alignment is observed for the K 0 S meson (spin ¼ 0) in Pb-Pb collisions and for the vector mesons in pp collisions. The measured spin alignment is unexpectedly large but qualitatively consistent with the expectation from models which attribute it to a polarization of quarks in the presence of angular momentum in heavy-ion collisions and a subsequent hadronization by the process of recombination.

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We present a study of the inclusive chargedparticle transverse momentum (p T) spectra as a function of charged-particle multiplicity density at mid-pseudorapidity, dN ch /dη, in pp collisions at √ s = 5.02 and 13 TeV covering the kinematic range |η| < 0.8 and 0.15 < p T < 20 GeV/c. The results are presented for events with at least one charged particle in |η| < 1 (INEL > 0). The p T spectra are reported for two multiplicity estimators covering different pseudorapidity regions. The p T spectra normalized to that for INEL > 0 show little energy dependence. Moreover, the highp T yields of charged particles increase faster than the charged-particle multiplicity density. The average p T as a function of multiplicity and transverse spherocity is reported for pp collisions at √ s = 13 TeV. For low-(high-) spherocity events, corresponding to jet-like (isotropic) events, the average p T is higher (smaller) than that measured in INEL > 0 pp collisions. Within uncertainties, the functional form of p T (N ch) is not affected by the spherocity selection. While EPOS LHC gives a good description of many features of data, PYTHIA overestimates the average p T in jet-like events.

Measurements of anisotropic flow coefficients (v n) and their cross-correlations using two-and multiparticle cumulant methods are reported in collisions of pp at ffiffi ffi s p ¼ 13 TeV, p-Pb at a center-ofmass energy per nucleon pair ffiffiffiffiffiffiffi ffi s NN p ¼ 5.02 TeV, Xe-Xe at ffiffiffiffiffiffiffi ffi s NN p ¼ 5.44 TeV, and Pb-Pb at ffiffiffiffiffiffiffi ffi s NN p ¼ 5.02 TeV recorded with the ALICE detector. The multiplicity dependence of v n is studied in a very wide range from 20 to 3000 particles produced in the midrapidity region jηj < 0.8 for the transverse momentum range 0.2 < p T < 3.0 GeV=c. An ordering of the coefficients v 2 > v 3 > v 4 is found in pp and p-Pb collisions, similar to that seen in large collision systems, while a weak v 2 multiplicity dependence is observed relative to nucleus-nucleus collisions in the same multiplicity range. Using a novel subevent method, v 2 measured with four-particle cumulants is found to be compatible with that from six-particle cumulants in pp and p-Pb collisions. The magnitude of the correlation between v 2 n and v 2 m , evaluated with the symmetric cumulants SCðm; nÞ is observed to be positive at all multiplicities for v 2 and v 4 , while for v 2 and v 3 it is negative and changes sign for multiplicities below 100, which may indicate a different v n fluctuation pattern in this multiplicity range. The observed long-range multiparticle azimuthal correlations in high multiplicity pp and p-Pb collisions can neither be described by PYTHIA 8 nor by impact-parameter-Glasma, MUSIC, and ultrarelativistic quantum molecular dynamics model calculations, and hence, provide new insights into the understanding of collective effects in small collision systems.